I'm just noticing that whenever I reboot Tvheadend won't recognize my tv adaptor immediately, I have to unplug the USB and plug it back in. Is this normal?
you have to enable the setting at the Tvh addon to wait for dvb adapter - I guess
If a new version of Libreelec is released do I need to reenter this command again?
If you connect to your box you have now at /storage/.config/modprobe.d/cx231xx.conf a file with some content. As long you don't delete this file it will work. It looks unlikely that this get "fixed" because it is not really a bug (more an misdesign of the hardware).